function Food(ele){
    //1.保存地图对象
    this.ele=ele
    //2.保存食物属性
    this.len=20
    this.foodObj=null
    this.foodX=0
    this.foodY=0
}
Food.prototype.create=function(){
    //行内元素需要宽高边距 display
    //1-创建div标签对象
    let divObj=document.createElement('div')
    //2-设置样式（w20/h20/bgreen/position:absolute）
    divObj.style.width=this.len+'px'
    divObj.style.height=this.len+'px'
    divObj.style.background='green'
    divObj.style.position='absolute'
    //单独保存食物的对象
    this.foodObj=divObj
    //3-在页面展示
    this.ele.appendChild(divObj)
    //4.默认移动食物
    this.move()
}
Food.prototype.move=function(){
    let foodXMaxNum=this.ele.clientWidth/this.len-1//40-1
    let foodYMaxNum=this.ele.clientHeight/this.len-1//20-1
    
    //随机公式：Math.floor(Math.random()*(max-min+1)+min)

    this.foodX=Math.floor(Math.random()*(foodXMaxNum-0+1)-0)*this.len
    this.foodY=Math.floor(Math.random()*(foodYMaxNum-0+1)-0)*this.len

    this.foodObj.style.left=this.foodX+'px'
    this.foodObj.style.top=this.foodY+'px'
}

